Optical networks, such as OTN (Optical transmission network), WDM (Wavelength-division multiplexing), SDH (Synchronous digital hierarchy) or SONET (Synchronous optical network), have been widely applied in the telecommunication field.
Recently, the automatic switched optical network (ASON) is one of research hotspots in the field of optical networks. The concept of ASON is offered by ITU-T G.8080, in which the function of ASON is achieved by setting a specific Control Plane (CP). ITU-T G.7713 specifies the framework to implement the distributed calls and connections in ASON to offer the implementation criterion for automatically establishing, modifying and deleting the calls and connections. Standards such as ITU-T G.7715 offer the implementation model and method for the route inquiry of the connection (the route inquiry described in the following will refer to the route inquiry of the connection, unless especially declared).
However, both the published ITU-T G.7715 and ITU-T G.7715.1 apply the model shown in FIG. 1. In this route model, when an ASON network element (NE for short) needs to query the connection route, the Connection Controller (CC) responsible for the connection control (including establishment, deletion, modification, and so on) sends the route inquiry request (Route Request for short) to the Route Controller (RC) responsible for the route inquiry and calculation, and then the RC calls a routing algorithm (a typical routing algorithm is Constrained Shortest Path First, shortly CSPF) according to the Route Request and calculates the route based on the Route Data Base (RDB) of the current node and returns the route inquiry result (Route Response for short) to the CC.
However, the RDB of a node generally is hard to have the complete route information of the whole ASON, especially when the ASON has several route domains. The RDB of one node always has only the information of local route domain. FIG. 2 shows the situation when one ASON has several route domains, which shows that when a connection should be established between A in route domain 1 and K in the route domain 4, as shown by the dot line, the model shown in FIG. 1 can not meet the requirement of the route inquiry and calculation of the connection.